Notifying a ul/dl configuration in lte tdd systems

ABSTRACT

A method for configuring a Time Division Duplex (TDD) Uplink/Downlink (UL/DL) allocation of a user equipment (UE) in a Long Term Evolution (LTE) network may include receiving an indicator, from an enhanced NodeB in the LTE network, on a physical channel identifying a TDD configuration for the UE and automatically updating the TDD UL/DL allocation of the UE in accordance with the TDD configuration.

TECHNICAL FIELD

This disclosure pertains to time division duplex configurations in LongTerm Evolution (LTE) environments.

BACKGROUND

In LTE systems, downlink and uplink transmissions may be organized intotwo duplex modes: frequency division duplex (FDD) mode and time divisionduplex (TDD) mode. The FDD mode uses a paired spectrum where thefrequency domain is used to separate the uplink (UL) and downlink (DL)transmission. FIG. 1A is a graphical illustration of an uplink anddownlink subframe separated in the frequency domain for the FDD mode. InTDD systems, an unpaired spectrum may be used where both UL and DL aretransmitted over the same carrier frequency. The UL and DL are separatedin the time domain. FIG. 1B is a graphical illustration of an uplink anddownlink subframe sharing a carrier frequency in the TDD mode.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a graphical illustration of an uplink and downlink subframeseparated in the frequency domain for the FDD mode.

FIG. 1B is a graphical illustration of an uplink and downlink subframesharing a carrier frequency in the TDD mode.

FIG. 2 is a schematic representation of an example wireless cellularcommunication system based on 3GPP LTE.

FIG. 3 is a schematic illustration of an example wireless station.

FIG. 4 is a schematic illustration of an example user equipment (UE).

FIG. 5A is an example process flowchart for MasterInformationBlock (MIB)message-based TDD configuration for the enhanced Node-B (eNB).

FIG. 5B is an example process flowchart for MIB message-based TDDconfiguration for the user equipment.

FIG. 6 is an example process flowchart for a mixed new release UE andlegacy UE scenario.

FIG. 7 is an example process flowchart for scrambling one or moreControl Format Indicator (CFI) code words with TDD configurationinformation.

FIG. 8A is an example process flowchart for new release user equipmentfor Physical Control Format Indicator Channel (PCFICH)-based TDDconfiguration.

FIG. 8B is an example process flowchart for legacy UEs for PCFICH-basedTDD configuration.

FIG. 9 is an example enhanced Node B process flowchart for PhysicalDownlink Control Channel (PDCCH)-based TDD configuration.

FIG. 10 is an example UE process flowchart for PDCCH-based TDDconfiguration.

DETAILED DESCRIPTION

An LTE TDD system may be enabled to notify a TDD UL/DL configuration (orconfiguration change) to the UE more frequently. The system may be ableto re-allocate the radio resource between UL and DL to meet requirementsassociated with, e.g., traffic conditions. In an LTE TDD system, asubframe of a radio frame can be a downlink (DL), an uplink (UL), or aspecial subframe. The special subframe comprises downlink and uplinktime regions separated by a guard period for downlink to uplinkswitching, and includes three parts: i) the downlink pilot time slot(DwPTS), ii) the uplink pilot time slot (UpPTS), and iii) the guardperiod (GP). Seven different UL/DL configuration schemes in LTE TDDoperations are listed in Table 1. In Table 1, D represents downlinksubframes, U is for uplink subframes and S is the special frame.

TABLE 1 LTE TDD Uplink-downlink configurations Downlink- to- UplinkUplink- Switch- downlink point Subframe number configuration periodicity0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U UD 2 5 ms D S U D D D S U D D 3 10 ms  D S U U U D D D D D 4 10 ms  D S UU D D D D D D 5 10 ms  D S U D D D D D D D 6 5 ms D S U U U D S U U DAs shown in Table 1, there are two switching point periodicitiesspecified in the LTE standard: 5 ms and 10 ms. The 5 ms switching pointperiodicity can support the co-existence between LTE and low-chip-rateUniversal Terrestrial Radio Access (UTRA) TDD systems, and 10 msswitching point periodicity can support the coexistence of LTE andhigh-chip-rate UTRA TDD systems. The supported configurations cover awide range of UL/DL allocations from a DL-heavy configuration (9:1 ratioDL:UL) to a UL heavy configuration (2:3 ratio DL:UL). TDD systems haveflexibility in terms of the proportion of resources assignable to uplinkand downlink communications within a given assignment of spectrum.Specifically, it is possible to distribute the radio resource unevenlybetween uplink and downlink to provide a way to utilize radio resourcesmore efficiently by selecting a UL/DL configuration based on, forexample, different traffic characteristics in DL and UL.

In some embodiments, the Master Information Block (MIB) may be used toindicate the TDD configuration. In some instances, there may be tenspare bits in the MIB. Some of the spare bits may be used for a TDDconfiguration indicator. In certain implementation, the MIB uses a fixedschedule (e.g., every 40 milliseconds), and communicating TDDconfiguration using the MIB spare bits can increase the TDDconfiguration identification frequency as fast as once every 40milliseconds, in certain embodiments.

In another example embodiment, the System Information Block Type 1(SIB1) can be updated when there is a need for a configuration change.When the system identifies a need for a configuration change, it canupdate the TDD-Config Information Element (IE) in SIB1 for the next 80millisecond transmission period. The UE can read the SIB1 every 80 ms.

In some embodiments, the TDD configuration indicator can be scrambledonto a control format indicator (CFI) on the physical control formatindicator channel (PCFICH). A current CFI code word can be scrambled bythe TDD configuration change indicator. Since the PCFICH is transmittedon a subframe basis, it will enable the dynamic change of the TDDconfiguration.

In some embodiments, a physical downlink control channel (PDCCH) can beused to notify the TDD configuration. A DCI format can be introducedthat will be transmitted on the common search space. A Radio NetworkTemporary Identifier (RNTI), called TDD-RNTI, may be used to scramblethe cyclic redundancy check (CRC) for the search purpose. The dynamicchange of the TDD configuration is provided because the PDCCH istransmitted every subframe.

In some embodiments, a dedicated signaling to connected mode UEs can beused. A dedicated signaling message (for example, a Radio ResourceControl (RRC) Connection Reconfiguration) containing a TDD-Config IE canbe used to communicate an updated TDD configuration to a connected modeUE. The network may send this dedicated message to all UEs in RRCconnected mode. In addition, the TDD configuration within SIB1 is alsoupdated in order to provide the information to idle mode UEs.

The user equipment described above may operate in a cellular network,such as the network shown in FIG. 2, which is based on the thirdgeneration partnership project (3GPP) long term evolution (LTE), alsoknown as Evolved Universal Terrestrial Radio Access (E-UTRA). Morespecifically, FIG. 2 is a schematic representation of an examplewireless cellular communication system 200 based on 3GPP LTE. Thecellular network system 200 shown in FIG. 2 includes a plurality of basestations 212. In the LTE example of FIG. 2, the base stations are shownas enhanced Node B (eNB) 212. It will be understood that the basestation may operate in any mobile environment, including femto-cell orpico-cell, or the base station may operate as a node that can relaysignals for other mobile and/or base stations. The example LTEtelecommunications environment 200 of FIG. 2 may include one or aplurality of radio access networks 210, core networks (CNs) 220 (shownas an Evolved Packet Core (EPC) 220), and external networks 230. Incertain implementations, the radio access networks may be EvolvedUniversal Mobile Telecommunications System (UMTS) terrestrial radioaccess networks (EUTRANs). In addition, in certain instances, corenetworks 220 may be evolved packet cores (EPCs). Further, there may beone or more user equipment 202 operating within the LTE system 200. Insome implementations, 2G/3G systems 240, e.g., Global System for Mobilecommunication (GSM), Interim Standard 95 (IS-95), Universal MobileTelecommunications System (UMTS) and CDMA2000 (Code Division MultipleAccess) may also be integrated into the LTE telecommunication system200.

In the example LTE system shown in FIG. 2, the EUTRAN 210 includes eNB212. UE 202 may operate in a cell serviced by one of eNB 212. The EUTRAN210 can include one or a plurality of eNBs 212 and one or a plurality ofUEs 202 can operate in a cell. The eNBs 212 communicate directly to theUEs 202. In some implementations, the eNB 212 may be in a one-to-manyrelationship with the UE 202, e.g., eNB 212 in the example LTE system200 can serve multiple UEs 202 within its coverage area, but each UE 202may be connected only to one eNB 212 at a time. In some implementations,the eNB 212 may be in a many-to-many relationship with the UEs 202. TheeNBs 212 may be connected to each other, and a UE handover may beconducted if a UE 202 travels from one eNB 212 to another eNB. UE 202may be any wireless electronic device used by an end-user tocommunicate, for example, within the LTE system 200. The UE 202 may bereferred to as mobile electronic device, user device, mobile station,subscriber station, or wireless terminal. UE 202 may be a cellularphone, personal data assistant (PDA), smart phone, laptop, tabletpersonal computer (PC), pager, portable computer, or other wirelesscommunications device.

In the uplink, an uplink data signal is transmitted via e.g., thePhysical Uplink Shared Channel (PUSCH), and an uplink control signal istransmitted via e.g., Physical Uplink Control Channel (PUCCH). In thedownlink, a synchronization signal is transmitted via, e.g.,Synchronization Channel (SCH), a downlink data signal is transmittedvia, e.g., Physical Downlink Shared Channel (PDSCH), and a downlinkcontrol signal is transmitted via e.g., Physical Downlink ControlChannel (PDCCH). A MasterInformationBlock (MIB) may be configured to betransmitted as broadcast information in each cell via e.g., a PhysicalBroadcast Channel (PBCH), and SystemInformationBlock (SIB) 1 to 11 areconfigured to be transmitted via e.g., PDSCH.

The MIB may be configured to include physical parameters such as a cellbandwidth and transmission antenna identification information, and asystem frame number (SFN), and is configured to be transmitted in aperiod of 40 ms. The SIB1 may be configured to be transmitted in aperiod of 80 ms.

Turning briefly to FIG. 3, each wireless station may be any electronicdevice operable to transmit and receive wireless signals in the LTEtelecommunication system 200. In the present disclosure, a wirelessstation can be either a mobile electronic device (e.g., UE) or a basestation (e.g., an eNB). FIG. 3 is a schematic illustration of an examplewireless station 300. A wireless station 300 may include a processor302, a memory 304, a wireless transceiver 306, and an antenna 308. Theprocessor 302 may comprise a microprocessor, central processing unit,graphic control unit, network processor, or other processor for carryingout instructions stored in memory 304. The functions of the processor302 may include computation, queue management, control processing,graphic acceleration, video decoding, and execution of a sequence ofstored instructions from the program kept in the memory module 304. Insome implementations, the processor 302 may also be responsible forsignal processing including sampling, quantizing, encoding/decoding,and/or modulation/demodulation of the signal. The memory module 304 mayinclude a temporary state device (e.g., random-access memory (RAM)) anddata storage. The memory module 304 can be used to store data orprograms (i.e., sequences of instructions) on a temporary or permanentbasis for use in a UE.

The wireless transceiver 306 can include both the transmitter circuitryand the receiver circuitry. The wireless transceiver 306 may beresponsible for converting a baseband signal to a passband signal orvice versa. The components of the wireless transceiver 306 may include adigital-to-analog converter/analog-to-digital converter, amplifier,frequency filter, and oscillator. In addition, the wireless transceiver306 may also include or be communicably coupled to a digital signalprocessing (DSP) circuitry 310 and a digital filter circuitry 312. TheDSP circuitry 310 may perform functionalities includes generatingOrthogonal Frequency Division Multiplexing (OFDM) and/or singlecarrier-frequency division multiple access (SC-FDMA) signals. OFDM is afrequency division multiplexing technology used as a multiple subcarriermodulation method. OFDM signal can be generated by modulating aninformation bearing signal, e.g., a sequence of bit-mapped symbols, onmultiple orthogonal subcarriers. Different bit-mapped symbols modulatedon different subcarriers may each be considered to experience a flatfading channel, i.e., the frequency response of a fading channel foreach subcarrier can be considered flat, such that the information may beeasier to decode at the receiver. In some practical implementations,OFDM uses fast Fourier transform (FFT) and inverse fast Fouriertransform (IFFT) to alternate between time and frequency domainrepresentations of the signal. The FFT operation can convert the signalfrom a time domain representation to a frequency domain representation.The IFFT operation can do the conversion in the opposite direction.While OFDM may be used in the radio downlink, SC-FDMA technology may beused in the radio uplink. SC-FDMA uses substantially similar modulationscheme as OFDM to modulate uplink signal to multiple subcarriers. Amongother differences with OFDM, a multi-point Discrete Fourier Transform(DFT) operation is performed before subcarrier mapping and IFFT inSC-FDMA on the transmitter side in order to reduce peak-to-average powerratio of the modulated signal. Since uplink signals are transmitted fromUEs, a lower peak-to-average power ratio of the modulated signal mayresult in a lower cost signal amplification at UEs.

The digital filter circuitry 312 may include an equalization filter thatis used for signal equalization. Equalization can be the process ofadjusting the balance between frequency components within a radiosignal. More specifically, equalizers may be used to render thefrequency response flat from the transmitter to the equalized output andwithin the entire channel bandwidth of interest. When a channel has beenequalized, the frequency domain attributes of the signal at theequalized output may be substantially similar to those of thetransmitted signal at the transmitter. An equalizer may include one ormore filter taps, each tap may correspond to a filter coefficient. Thefilter coefficients may be adjusted according to the variation ofchannel/system condition.

The antenna 308 is a transducer which can transmit and/or receiveelectromagnetic waves. Antenna 308 can convert electromagnetic radiationinto electric current, or vice versa. Antenna 308 is generallyresponsible for the transmission and reception of radio waves, and canserve as an interface between the transceiver 306 and the wirelesschannel. In some implementations, the wireless station 300 may beequipped with more than one antenna to take advantage ofmultiple-input-multiple-output (MIMO) technology. MIMO technology mayprovide a process to utilize multiple signal paths to reduce the impactof multipath fading and/or to improve the throughput. By using multipleantennas at a wireless station, MIMO technology may enable atransmission of multiple parallel data streams on the same wirelesschannel, thereby increasing the throughput of the channel.

Returning to the illustration of FIG. 2, UEs 202 may transmit voice,video, multimedia, text, web content and/or any otheruser/client-specific content. On the one hand, the transmission of someof these contents, e.g., video and web content, may require high channelthroughput to satisfy the end-user demand. On the other hand, thechannel between UEs 202 and eNBs 212 may be contaminated by multipathfading, due to the multiple signal paths arising from many reflectionsin the wireless environment. Accordingly, the UEs' transmission mayadapt to the wireless environment. In short, UEs 202 generate requests,send responses, or otherwise communicate in different means with EvolvedPacket Core (EPC) 220 and/or Internet Protocol (IP) networks 230 throughone or more eNBs 212.

A radio access network (RAN) is part of a mobile telecommunicationsystem which implements a radio access technology, such as UMTS,CDMA2000 and 3GPP LTE. In many applications, the RAN included in an LTEtelecommunications system 200 is called an EUTRAN 210. The EUTRAN 210can be located between UEs 202 and EPC 220. The EUTRAN 210 includes atleast one eNB 212. The eNB can be a radio base station that may controlall or at least some radio related functions in a fixed part of thesystem. The at least one eNB 212 can provide radio interface withintheir coverage area or a cell for UEs 202 to communicate. eNBs 212 maybe distributed throughout the cellular network to provide a wide area ofcoverage. The eNB 212 directly communicates with one or a plurality ofUEs 202, other eNBs, and the EPC 220.

The eNB 212 may be the end point of the radio protocols towards the UE202 and may relay signals between the radio connection and theconnectivity towards the EPC 220. In certain implementations, the EPC220 is the main component of a core network (CN). The CN can be abackbone network, which may be a central part of the telecommunicationssystem. The EPC 220 can include a mobility management entity (MME), aserving gateway (SGW), and a packet data network gateway (PGW). The MMEmay be the main control element in the EPC 220 responsible for thefunctionalities comprising the control plane functions related tosubscriber and session management. The SGW can serve as a local mobilityanchor, such that the packets are routed through this point for intraEUTRAN 210 mobility and mobility with other legacy 2G/3G systems 240.The SGW functions may include the user plane tunnel management andswitching. The PGW may provide connectivity to the services domaincomprising external networks 230, such as the IP networks. The UE 202,EUTRAN 210, and EPC 220 are sometimes referred to as the evolved packetsystem (EPS). It is to be understood that the architectural evolvementof the LTE system 200 is focused on the EPS. The functional evolutionmay include both EPS and external networks 230.

Though described in terms of FIGS. 2-3, the present disclosure is notlimited to such an environment. In general, cellular telecommunicationsystems may be described as cellular networks made up of a number ofradio cells, or cells that are each served by a base station or otherfixed transceiver. The cells are used to cover different areas in orderto provide radio coverage over an area. Example cellulartelecommunication systems include Global System for Mobile Communication(GSM) protocols, Universal Mobile Telecommunications System (UMTS), 3GPPLong Term Evolution (LTE), and others. In addition to cellulartelecommunication systems, wireless broadband communication systems mayalso be suitable for the various implementations described in thepresent disclosure. Example wireless broadband communication systemincludes IEEE 802.11 wireless local area network, IEEE 802.16 WiMAXnetwork, etc.

Turning briefly to FIG. 4, each UE 202 may be any electronic deviceoperable to receive and transmit wireless signals in the LTEtelecommunication system 200. FIG. 4 is a schematic illustration of anexample user equipment (UE) 202. UE 202 may include a processor 402, amemory 404, a wireless transceiver 406, and an antenna 408. Theprocessor 402 may comprise a microprocessor, central processing unit,graphic control unit, network processor, or other processor for carryingout instructions stored in memory 404. The functions of the processor402 may include computation, queue management, control processing,graphic acceleration, video decoding, and execution of a sequence ofstored instructions from the program kept in the memory module 404. Insome implementations, the processor 402 may also be responsible forsignal processing including sampling, quantizing, encoding/decoding,and/or modulation/demodulation of the signal. The memory module 404 mayinclude a temporary state device (e.g., random-access memory (RAM)) ordata storage. The memory module 204 can be used to store data orprograms (i.e., sequences of instructions) on a temporary or permanentbasis for use in a UE. The wireless transceivers 406 can include boththe transmitter circuitry and the receiver circuitry. The wirelesstransceivers 406 may be responsible for up-converting a baseband signalto a passband signal, or vice versa. The components of wirelesstransceivers 406 may include a digital-to-analogconverter/analog-to-digital converter, amplifier, frequency filter andoscillator. The antenna 408 is a transducer which can transmit and/orreceive electromagnetic waves. Antenna 408 can convert electromagneticradiation into electric current, or vice versa. Antenna 408 is generallyresponsible for the transmission and reception of radio waves, and canserve as the interface between the transceiver 406 and the wirelesschannel.

The LTE network environment and UE described above in relation to FIGS.2-4 may function to dynamically identify or update TDD configurationinformation. In an embodiment, a method for configuring a Time DivisionDuplex (TDD) UL/DL allocation in a UE in an LTE network can includereceiving, at a predefined period, during a connected state, eachinformation block transmitted by an enhanced NodeB (eNB) in the LTEnetwork, wherein each information block is transmitted in accordancewith a fixed schedule having a predefined transmission period andincludes information identifying a TDD configuration. The UE maydetermine that an updating of the TDD configuration is requested orrequired based, at least in part, on the information identifying the TDDconfiguration in the information block, the information identifying theTDD configuration indicating an updated TDD configuration. In responseto at least identifying the updated TDD configuration, the UE canautomatically update the TDD UL/DL allocation of the UE in accordancewith the updated TDD configuration.

The information block transmitted may be in a System Information BlockType 1 (SIB1) or a MasterInformationBlock (MIB). The MIB uses a fixedschedule with a periodicity of 40 ms and repetitions made within 40 ms.The first transmission of the MIB is scheduled in subframe 0 of radioframes for which the System Frame Number (SFN) mod 4=0, and repetitionsare scheduled in subframe 0 of all other radio frames. The newTDD-Config information can be applied as quickly as at the beginning ofthe next 40 ms MIB period. In certain example implementations, there maybe ten “spare” bits in the MIB. An example MIB structure without theTDD-Config bits is provided below:

 -- ASN1START MasterInformationBlock ::= SEQUENCE {  dl-Bandwidth ENUMERATED {   n6, n15, n25, n50, n75, n100},  phich-Config PHICH-Config,  systemFrameNumber  BIT STRING (SIZE (8)),  spare  BITSTRING (SIZE (10)) } -- ASN1STOPIn certain embodiments, the MIB may be updated to include the TDDconfiguration. Three bits may be used from the “spare” bits to representseven TDD configurations. An example MIB structure that includes the TDDconfiguration bits is shown below:

-- ASN1START MasterInformationBlock ::= SEQUENCE {  dl-Bandwidth ENUMERATED {   n6, n15, n25, n50, n75, n100},  phich-Config PHICH-Config,  systemFrameNumber  BIT STRING (SIZE (8)),  tdd-Config BIT STRING (SIZE (3)),  OPTIONAL,-- Cond TDD  spare  BIT STRING (SIZE(7)) } -- ASN1STOPIn certain embodiments, two bits may be used to indicate a change of TDDconfigurations by limiting the choices of such change (i.e., tdd-ConfigBIT STRING (SIZE (2)). For example, if the new TDD configuration has thesame switching periodicity as the current TDD configuration, then thetotal number of configurations can be divided into two groups, andwithin each group there are at most four configurations (see Table 2 fordetails). Thus, two bits are enough to indicate a change in TDDconfigurations. Similarly, one bit can be used to indicate a move fromone configuration to another, adjacent configuration. For example, ifthe existing configuration is configuration “1,” one bit is sufficientto indicate a move down to configuration “2” or a move up toconfiguration “6,” based on the organization of the TDD configurationsshown in Table 2 below. Generally, the term “TDD configuration change”can include an indication of a new TDD configuration or an indication inwhether/how to change the TDD configuration.

When the MIB message is used to identify a TDD configuration, newrelease UEs receive and understand it and change the configurationaccordingly at next frame. New release UEs may operate in accordancewith this disclosure, and legacy UEs may operate in accordance withRelease 10 and earlier. Legacy UEs might not attempt to decode the last10 bits of the bit string, so legacy UEs may keep the same configurationas before. It is possible that when the TDD configuration is changed,the system also updates the TDD configuration information in SIB1 basedon a modification period. The system can then trigger a systeminformation modification notification procedure. Therefore, the legacyUEs will eventually update the configuration in the next modificationperiod. If there are multiple configuration changes during the (minimum)640 ms modification period, the most recent change will be applied. As aresult, the legacy UEs will also change the TDD configuration to anupdated configuration

If the configuration change is very frequent, it is not always necessaryto make the legacy UE to follow up with the change via SIB1 informationchange. The system can keep tracking the configuration change rate (CCR)for every given period, e.g., 640 ms. If the CCR is less than a certainpre-defined threshold, T_(CCR), the system may update the TDDconfiguration information in SIB1, and the system informationmodification notification procedure will follow. Otherwise, the systemdoes not update the SIB1. In this example implementation, the system cansave system radio resource and batter power for legacy UEs. Interferenceissues between new and legacy (“inter-release”) UEs (especially wherethe inter-release UEs are located very close to each other) may occurduring the time duration of subframes which are switched from UL to DL.The UL/DL configurations can be divided into two groups in terms of theswitching point periodicity in ascending order based on the number of DLsubframes: one group with the periodicity of 5 ms (configurations 0, 1,2, 6 of Table 2), and one group with the periodicity of 10 ms(configurations 3, 4, 5 of Table 1). Table 2 shows how the sevenconfigurations can be grouped.

TABLE 2 UL/DL configuration groups Downlink- to- Uplink Uplink- Switch-downlink point Subframe number configuration periodicity 0 1 2 3 4 5 6 78 9 Group One 0 5 ms D S U U U D S U U U 6 5 ms D S U U U D S U U D 1 5ms D S U U D D S U U D 2 5 ms D S U D D D S U D D Group Two 3 10 ms  D SU U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D D DDThe candidate configurations are limited to the same group of thecurrent configuration of the UE. In this way, the number of subframeswith a link direction change will be relatively small. Moreover, the eNBmay not grant any UL transmissions for legacy UEs atlink-direction-conflict subframes in subsequent frames. For example, ifthe current configuration is 0 and the system decides to change toconfiguration 6, the eNB should deny any UL grant at subframe 9 insubsequent frames. For UL control signal transmission and non-adaptiveretransmission, they will be transmitted without UL grant.

For TDD LTE systems, Sounding Reference Signal (SRS) is transmitted atone or both symbols in UpPTS, which is not changed as the configurationchange. The eNB knows where to detect sounding reference signals.

Physical Uplink Control Channel (PUCCH) transmission: Given the factthat there is no data transmission (UL grant denied) and re-transmission(see below regarding hybrid automatic repeat request (HARM)retransmission handling), the Physical Uplink Control Channel (PUCCH)only transmission of legacy UEs will be placed at the frequency edges ofthe bandwidth. Moreover, periodic channel state parameters for legacyUEs, including channel quality indicators, precoding matrix indices,and/or rank indicators, can also be scheduled in the UL subframe thatdoes not change within a configuration group. Only those subframes withlink direction change at these frequency edges will cause aninterference issue. The number of trouble subframes is very limited, sothe eNB should be able to avoid scheduling nearby new release UEs atthis frequency edges for the time of subframe with link directionchange.

HARQ retransmission handling: The eNB may check if there is/will be aretransmission at the time of link direction change subframes beforesending out the configuration change indicator. If so, it should deferthe configuration change.

SPS scheduling: In the case of UL transmission at the direction conflictsubframe due to SPS scheduling, eNB can do one of the following:reconfigure the SPS by sending an sps-Config message (existing IERadioResourceConfigDedicated); or defer the configuration change as thesame used in the HARQ handling.

DRX: For MIB and SIB1-based techniques, it requires the UE to readconfiguration information from MIB or SIB1 upon every wakeup so the UEknows the current configuration. MIB is transmitted on a physicalchannel, specifically, the physical broadcast channel (PBCH). The way itis designed such that every transmission is self-decodable. Most likely,UE will likely detect the MIB on the first subframe 0 transmission. SIB1is always scheduled on subframe 5, and it is also self-decodable on eachtransmission. If the first subframe is not subframe 0 (when using MIBfor TDD configuration) or subframe 5 (when using SIB1 for TDDconfiguration), when UE wakes up, or if the UE is not able tosuccessfully detect the current configuration on first transmission, apredefined configuration can be assumed. For example, configuration 2(for 5 ms periodicity group) or configuration 5 (for 10 ms periodicitygroup) should be temporarily assumed until the current configuration isdetected. The reason is that configuration 2 and 5 have the fewest ULsubframes and will not cause interference to other UEs due to thedirection conflict.

After transitioning from a Discontinuous Reception (DRX) mode or an idlemode to a connected mode, a UE may have a delay to receive the systeminformation block identifying the TDD configuration. The UE canautomatically update the TDD UL/DL allocation to a predefined TDDconfiguration in response to the delay. The UE can update the TDD UL/DLallocation to the defined TDD configuration as soon as the UE receivessystem information block.

Paging and the Physical Random Access Channel (PRACH) are unaffected byusing MIB for transmitting TDD configurations. For paging, the LTE TDDuses subframe 0, 1, 5, and 6 for paging. These subframes are always forDL regardless of the configuration. For PRACH, the LTE TDD introducesShort RACH known as format 4. It is always transmitted on the UpPTS,which is in the special subframe and will not change direction as theconfiguration changes.

In some embodiments, when the configuration changes, the system willpage the connected UEs for a system information change notification. Theconnected UEs reads the new configuration. Idle UEs will not try toreceive the system information each modification period. Therefore, theidle UEs' battery efficiency may not be impacted. However, this schemerequires the network to differentiate the paging to connected and idleUEs. It will lead to a more complex paging mechanism. A new Paging RNTI(P-RNTI) may be introduced for this purpose.

In some embodiments, the connected UE can read MIB every 40 ms. Doing socomes at the expense of extra power consumption. It may be understoodthat the UE power consumption is mainly on the RF transceiver chain, thebaseband processing consumes just a small portion of the total power.The power consumption increase should not be significant for thisprocess.

FIG. 5A is an example process flowchart for MasterInformationBlock (MIB)message-based TDD configuration for the enhanced Node-B (eNB). For agiven period (e.g., 40 ms for MIB, 80 ms for SIB1), the traffic periodmay be monitored 502. The TDD Configuration may be identified and setbased on the monitored traffic 504. A determination may be made as towhether the identified TDD configuration information from the monitoredtraffic is different from the existing TDD configuration used by UEs incommunication with the eNB 506. If the identified TDD configuration isdifferent, the TDD configuration can be communicated to the UEs usingthe MIB or SIB1. Specifically, a TDD-Config field of the MIB or SIB1 canbe updated with the new TDD configuration information 508. If the TDDconfiguration information is not new or different, the traffic canreturn to 502 to continue to be monitored and TDD configurationinformation can be identified without updating the MIB or SIB1TDD-Config field until a different TDD configuration is identified.

FIG. 5B is an example process flowchart 550 for MIB or SIB1message-based TDD configuration for the user equipment. A determinationmay be made as to the UE's connection mode 554. For UEs that are notidle (i.e., connected UEs), a determination is made whether the UE is inDRX mode 556. For UEs not in DRX mode, the UEs may be able to pick upnew configuration from MIB or SIB1 558. For UEs in DRX, the UE updatesthe new configuration using the MIB or SIB1 when it wakes up or entersan awake period (or a period within the awake period) 560. For UEs inidle state, they will update the configuration based on the MIB or SIB1whenever they become connected or enter a connected mode 562. For UEs inDRX or for idle UEs, if there is a delay in identifying a new TDDconfiguration 564 (e.g., the first subframe does not contain MIB or SIB1when UE wakes up, or if the UE is not able to successfully detect thecurrent configuration on first transmission (e.g., because ofinterference)), configuration 2 (for 5 ms periodicity group) or 5 (for10 ms periodicity group) may be temporarily assumed until the currentconfiguration is detected 566. This temporary period may be brief sincethe MIB retransmission is every frame and SIB1 retransmission is everyother frame. If there is no delay, or after the expiration of the delay,the identified TDD configuration can be used 568.

Note that the given period in FIGS. 5A-B is normally set as 40 ms or 80ms, but the period may be a configurable parameter for embodiments wherethe UE reads MIB less frequently (e.g. every 120 ms, or 160 ms).

FIG. 6 is an example process flowchart 600 for a mixed new release UEand legacy UE scenario. For a given time period (e.g., 40 ms for MIB, 80ms for SIB1), the traffic is monitored 602. A TDD configuration can beidentified based on the traffic 604. A determination may be made as towhether the identified TDD configuration is different from the TDDconfiguration used at that time by the UEs 606. If the identified TDDconfiguration is different from the TDD configuration used at the timeby the UEs, the information block can be updated with the new TDDconfiguration 608. The MIB can be updated at the start of the next 40 msperiod; the SIB1 can be updated at the start of the next 80 ms period.For example, the TDD-Config field of the MIB can be updated with bitsrepresenting the new TDD configuration or a change in the TDDconfiguration. The configuration change rate (CCR) can be updated 610.In certain implementations, the system can initiate handling ULtransmissions, HARQ Retransmission, and Control Signaling Transmissionfor legacy UEs on directional conflict subframes 611.

The system can keep tracking the CCR for every given period. The CCR canbe compared to the T_(CCR) 612. If the CCR is less than certainpre-defined threshold, T_(CCR), the system may update the TDDconfiguration information in SIB1 614, and the system informationmodification notification procedure can follow 618. If the CCR isgreater than T_(CCR), 616, the system can continue monitoring traffic602 without updating the TDD configuration for Legacy UEs.

In certain embodiments, the SIB1 may be used for TDD configuration. SIB1uses a fixed schedule with a periodicity of 80 ms and repetitions madewithin 80 ms. The first transmission is scheduled in subframe 5 of radioframes for which the SFN mod 8=0, and repetitions are scheduled insubframe 5 of all other radio frames for which SFN mod 2=0. The new TDDconfiguration information can be applied as quickly as at the beginningof the next 80 ms SIB1 period. The SIB1 technique is similar to theMIB-based technique. Using SIB1 provides a lower maximum configurationchange rate.

In some embodiments, a method for configuring a Time Division Duplex(TDD) UL/DL allocation of a user equipment (UE) in a Long Term Evolution(LTE) network includes receiving an indicator, from an eNB in the LTEnetwork, on a physical channel identifying a TDD configuration for theUE. A physical channel is a transmission channel that conveys user dataand control messages on the physical layer. The TDD configurationinformation is embedded or multiplexed onto it. The TDD UL/DL allocationof the UE may be automatically updated in accordance with the TDDconfiguration. The Physical Control Format Indicator Channel (PCFICH) iscurrently used to indicate the number of OFDM symbols used fortransmission of PDCCHs in each subframe. It is called Control FormatIndicator (CFI). A TDD configuration or configuration change informationcan be carried over the CFI to be used to update TDD configuration.There are three different CFI code words used in the current version ofLTE and a fourth one is reserved for future use as shown in Table 3.Each code word is 32 bits in length.

TABLE 3 CFI Code Words CFI code word CFI <b₀, b₁, . . . , b₃₁> 1 <0, 1,1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1,1, 0, 1, 1, 0, 1> 2 <1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0,1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0> 3 <1, 1, 0, 1, 1, 0, 1, 1,0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1>4 <0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,0, 0, 0, 0, 0, 0, 0, 0, 0> (Reserved)The CFI code word may be scrambled by the TDD configuration orconfiguration change indicator. In some embodiments, seven configurationindicator values can be used. Each value may correspond to one UL/DLconfiguration listed in Table 1. As a result, there can be as many as 21different CFI code words at the end. This may decrease the minimaldistance of the code word. At the UE side, after detecting the signal onthe PCFICH, UE will descramble the received code word to recover theoriginal CFI value.

In some embodiments, two configuration change indicator values can beused. Each value corresponds to either a move-up or a move-down in theTDD configuration group. The configurations can be divided into twogroups in terms of switching periodicity, and organized into ascendingorder in terms of number of DL subframes, as in Table 2 above. One groupis configuration [0, 6, 1, and 2] and the other is [3, 4, and 5]. When aUE detects a move-up indicator, it will change the configuration to onelevel up to the current level, e.g., from configuration 1 to 6 in groupone. If it receives a move-down indicator, it will change to one leveldown to the current level, e.g. from configuration 6 to 1.

An example of the implementation of two-value configuration changeindicator is as follows. We take the first six bits from each CFI codeword (1, 2, 3), and perform binary “+1” and “−1” on each of themrespectively. Each code word can be extended to 32 bits using the samerepetition code as in the current LTE specification. Examples of theresulting nine code words are shown in Table 4.

TABLE 4 Examples of CFI Code Words for TDD Configuration CFI1 + 1: [0,1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0,1, 1, 1, 0, 0, 0, 1] CFI1 − 1: [0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0,1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1] CFI2 + 1: [1,0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1,0, 1, 1, 1, 0, 1, 0] CFI2 − 1: [1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1,0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0] CFI3 + 1: [1,1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1,1, 0, 1, 1, 1, 1, 1] CFI3 − 1: [1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1,1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1]One CFI value has three code words associated with it. They representconfiguration move-up a level, move-down a level, and no change,respectively. Table 5 shows an example of CFI code words.

TABLE 5 Examples of CFI Code Words Corresponding to TDD ConfigurationChanges TDD CFI code word configuration CFI <b₀, b₁, . . . , b₃₁> change1 <0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0, 0, 0, 1, 1, 1, 0,0, 0, 1, 1, 1, 0, 0, 0, 1> Move-up 1 <0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1,1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1> Unchanged1 <0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 1, 0, 1,0, 0, 1, 1, 0, 1, 0, 0, 1> Move-down 2 <1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1,0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0> Move-up 2<1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1,1, 0, 1, 1, 0, 1, 1, 0> Unchanged 2 <1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0,1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0> Move-down 3<1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 1, 1,1, 1, 0, 1, 1, 1, 1, 1> Move-up 3 <1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0,1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1> Unchanged 3<1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1,1, 1, 0, 1, 0, 1, 1, 1> Move-down 4 <0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0> (Reserved)FIG. 7 is an example process flowchart 700 for scrambling one or moreCFI code words with TDD configuration information. An original code wordcan be identified 702. The system may check whether a configurationchange indication was received 704. If no configuration changeindication was received, the system can transmit the original CFI codeword 706. If a “move-down” indication was received 708, a check may beperformed as to whether the current TDD configuration is already set toconfiguration 2 or 5 (of Table 2 above) 708. If a move-down indicationwas received (i.e., DL heavier), and the TDD configuration is already inconfiguration 2 or 5, the eNB will not instruct any configuration changeto UEs, and the system may transmit the original CFI code word 706. If aconfiguration change indicator was received, and the configuration isnot one of configurations 2 or 5, the identified CFI code word can bescrambled with the move-down indicator 710. The scrambled CFI code wordcan be transmitted 712, and the TDD-Config field of SIB1 can be updatedwith the new TDD configuration 714. If the received configuration changeindication is a “move-up” indication (i.e., UL heavier), a check may beperformed as to whether the configuration is set to configuration 0 or 3(of Table 2 above) 716. If a configuration change indicator wasreceived, and the TDD configuration is set to configuration 0 or 3, theeNB will not instruct any configuration change to UEs, and the originalCFI code word can be transmitted 706. If a configuration changeindicator was received, and the TDD configuration is not in one ofconfigurations 0 or 3, the identified CFI code word can be scrambledwith the move-up indicator 718. The scrambled CFI code word can betransmitted 712, and the SIB1 can be updated with the new TDDconfiguration information 714.

There are various embodiments for the move-up and move-down indicators.An error-correcting coding scheme can be also used instead of thecurrent repetition code to increase the reliability of CFI code wordtransmission. Moreover, if there is error in detection, the UE will havean opportunity to correct it from the regular system information changenotification procedure via updated SIB1. Thus, the risk of propagatingthe error can be diminished.

FIG. 8A is an example process flowchart 800 for new release UEs forPCFICH-based TDD configuration. At the UE, for new release UEs 802,after detecting the CFI code word 804, UE may adjust the configurationaccordingly 806. FIG. 8B is an example process flowchart 850 for legacyUEs for PCFICH-based TDD configuration. For legacy UEs 852, the originalCFI code word will be detected based on minimum distance as shown inTable 5 854. The TDD configuration can be updated via normal systeminformation change procedure 856.

The LTE TDD system may change the TDD configuration at the frequency ofevery frame. The eNB may use the same configuration change indicator inthe duration of each frame to scramble the CFI value. The UE will detectthe same configuration change indicator during the frame. Doing so mayincrease the robustness of detection.

In some embodiments, the TDD configuration is changed every DL subframe.The eNB may use an independent configuration change indicator in everysubframe to scramble the CFI value. This scheme requires carefulcoordination of other system processes, such as HARQ, interference, etc.

The PCFICH-based TDD configuration also allows legacy UEs operating asnormal because the PCFICH detection is minimum distance based. Althoughthe legacy UE is not able to recognize the new CFI code word in Table 5,it will be able to detect the original CFI code word from the new CFIcode words based on the minimum distance. Therefore, it will continue tooperate as normal. The side issues of UL transmission, HARQretransmission and control signalling transmission for legacy UEs, etc.,may operate in a similar manner as described above for MIB-based TDDconfiguration.

In certain embodiments, the PDCCH may be used for TDD configuration. ThePDCCH channel carries a Downlink Control Information (DCI). It supportsmultiple formats and the UE needs to search and blindly detect theformat of the PDCCHs. Search spaces have been defined in the LTEspecification. It describes the set of CCEs the UE is required tomonitor. There are two types of search spaces: common search space andUE-specific search space. The common search space carries the commoncontrol information and is monitored by all UEs in a cell. A new DCIformat, called Format TDDConfig, may be transmitted on the common searchspace. A new Radio Network Temporary Identifier called TDD-RNTI, is usedto scramble the CRC of Format TDDConfig. TDD-RNTI can be defined. Forexample, we can define TDD-RNTI value as shown in Table 6 based onavailability.

TABLE 6 TDD-RNTI Value (hexa-decimal) RNTI FFFC TDD-RNTIFor seven TDD configurations (e.g., those defined above in Table 1),three bits is sufficient to represent all the configurations. In certainembodiments, the three bits will be appended by sixteen-bit scrambledCRC. To increase the robustness of error protection, one can encode thethree bits with a simple forward error correction (FEC) code, such asrepetition code or Bose and Ray-Chaudhuri (BCH) code, etc. The code wordafter encoder will be the payload of DCI format TDD-Config. As anexample, to make the size comparable to other DCI format (payload sizeis different with respect to the number of antenna and the bandwidth) onthe common search space, Table 7 shows the payload of DCI formatTDDConfig by using nine-time repetition code, which is twenty-sevenbits. Then the 27-bit code word will be appended by the scrambled CRC.

TABLE 7 DCI Format TDDConfig Field Bits TDD Configuration Indicator 27(3 bits repeated 9 times)The scrambled CRC is obtained by performing a bit-wise exclusive or(XOR) operation between the 16-bit CRC and the 16-bit TDD-RNTI (FFFC).Therefore, the total number of bits for DCI Format TDDConfig isforty-three. Given the fact that the PDCCH on the common search space isat least at aggregation level four, after channel coding, the final coderate will be very low. This will provide an excellent possibility ofcorrect detection. For PDCCH-based TDD configuration, the information UEreceives can be a configuration indicator which directly represents theconfiguration. This will provide more flexibility on configurationchoice. It can also be the configuration change indicator which onlyneeds one bit to represent it.

FIGS. 9 and 10 show the implementation of proposed PDCCH-based techniqueat the eNB and UE. FIG. 9 is an example enhanced Node B processflowchart 900 for PDCCH-based TDD configuration. A DCI format TDD-Configcan be defined 902. The CRC bits may be scrambled using the TDD-RNTI andattached to a payload 904. Then, a tail-biting convolutional coding maybe performed. The coded stream is rate-matched to a predefined the ratevia puncturing or padding some bits. The channel can be coded, and arate matching procedure can be implemented 906. The payload along withthe scrambled CRC bits are transmitted on a common search space of thePDCCH 908.

FIG. 10 is an example UE process flowchart 1000 for PDCCH-based TDDconfiguration. The UE may receive a payload. The channel may be decodedfollowing a rate matching procedure 1002. The PDCCH may be searchedbased on the scrambled TDD-RNTI 1004.

For PDCCH and PCFICH-based techniques, the TDD configuration detectiondelay issue is alleviated since the configuration information isembedded in every DL subframe.

New release TDD UEs can search for the DCI Format TDD-Config and detectthe TDD configuration in addition to the existing search rules. If thereare no legacy UEs in the network, all served UEs will change to the newconfiguration at the same time. For legacy UEs, however, the UEs followthe existing search rules and do not have ability to detect the new TDDconfiguration. As mentioned in the previously, the legacy UE will updatethe TDD configuration using the standard system information changeprocedure through SIB1. If there are legacy UEs in the network,inter-release UE interference can be addressed in a similar fashion asdescribed above.

The TDD configuration change can be at the frequency of every frame. Forexample, the eNB can use the same TDD configuration in DCI FormatTDDConfig in the duration of each frame. The UE can detect the sameconfiguration or configuration change indicator at each subframe duringthe frame, which can increase the robustness of detection. In certainembodiments, the eNB can use the same TDD configuration in DCI FormatTDD-Config in the duration of each frame; however, it may not betransmitted on each DL or special subframe, it may only be transmittedin a few DL or special frames e.g., only in subframe 0, or only on twospecial frames, etc. Doing so may alleviate the load of PDCCH. In someimplementations, the TDD configuration indicator can be sent every DLsubframe. For example, the eNB can use different TDD configuration inDCI Format TDD-Config in the duration of each subframe. This schemerequires careful coordination of other system processes, such as HARQ,interference, etc. The TDD-Config information element (IE) is in SIB1and RadioResourceConfigCommon IE. As mentioned above, the UE may onlyread SIB1 once every 640 ms due to the accommodation of DRX of idle UEs.The increase of SIB1 reading frequency will represent the UE powerconsumption increase. This increase is significant since it involves theRF transceiver chain. Therefore, a possible message-based TDDconfiguration indication may use an RRC connection reconfigurationprocedure. If a TDD reconfiguration is needed, the TDD-Config IE can bechanged to represent a desired configuration. The RRC connectionreconfiguration procedure can be initiated, including themobilityControlInfo (it contains RadioResourceConfigCommon IE, which hasthe new TDD-Config) to UEs in RRC Connected state. The SIB1 may beupdated with the new configuration. It is to be understood that the RRCmessage is an example. A new procedure may be defined, e.g., TDDreconfiguration procedure, and introduce a new message. Idle UEs mayobtain the current configuration when it becomes connected via SIB1.

Using a dedicated signal for TDD configuration is backwards compatiblebetween new release UEs and legacy UEs. In certain embodiments, a newprocedure may be introduced (e.g., the TDD reconfiguration procedure),which sends a message only to communicate the TDD-Config IE to theconnected UE.

Using a dedicated signal can be used as a supplementary TDDconfiguration technique in addition to other techniques described hereinfor dealing with the legacy UE configuration change. In this way, thelegacy UE does not have to wait for modification period of 640 ms. Itcan change the configuration within 20 ms.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of what may beclaimed, but rather as descriptions of features specific to particularimplementations. Certain features that are described in thisspecification in the context of separate implementations can also beimplemented in combination in a single implementation. Conversely,various features that are described in the context of a singleimplementation can also be implemented in multiple implementationsseparately or in any suitable subcombination. Moreover, althoughfeatures may be described above as acting in certain combinations andeven initially claimed as such, one or more features from a claimedcombination can in some cases be excised from the combination, and theclaimed combination may be directed to a subcombination or variation ofa subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the implementations described above should not beunderstood as requiring such separation in all implementations, and itshould be understood that the described program components and systemscan generally be integrated together in a single software product orpackaged into multiple software products.

Thus, particular implementations of the subject matter have beendescribed. Other implementations are within the scope of the followingclaims. In some cases, the actions recited in the claims can beperformed in a different order and still achieve desirable results. Inaddition, the processes depicted in the accompanying figures do notnecessarily require the particular order shown, or sequential order, toachieve desirable results. In certain implementations, multitasking andparallel processing may be advantageous.

1. A method for configuring a Time Division Duplex (TDD) Uplink/Downlink(UL/DL) allocation of a user equipment (UE) in a Long Term Evolution(LTE) network, comprising: receiving an a TDD configuration changeindicator, from an enhanced NodeB in the LTE network, on a physicalchannel, identifying a TDD configuration change for the UE; andautomatically updating the TDD UL/DL allocation of the UE in accordancewith the TDD configuration change identified by the TDD configurationchange indicator.
 2. The method of claim 1, wherein the physical channelcomprises a Physical Control Format Indicator Channel (PCFICH), themethod further comprising: identifying a scrambled Control FormatIndicator (CFI) based, at least in part, on the received PCFICH; anddescrambling the scrambled CFI to identify the CFI and the indicator,wherein the TDD UL/DL allocation is updated in accordance with the TDDconfiguration change identified in the received indicator.
 3. The methodof claim 1, further comprising determining a TDD UL/DL allocationcorresponding to one of a plurality of TDD UL/DL configurations based onthe received TDD configuration change indicator.
 4. The method of claim3, further comprising determining the TDD UL/DL configurationcorresponding to a value indicating a move-up or a move down in one oftwo TDD configuration groups.
 5. The method of claim 4, wherein the twoTDD configuration groups include a first group having a first switchingperiodicity and a second group having a second switching periodicitylonger than the first switching periodicity.
 6. The method of claim 5,wherein the first group and the second group are arranged in ascendingorder in terms of number of DL subframes.
 7. The method of claim 5,wherein the first switching periodicity is five milliseconds and thesecond switching periodicity is ten milliseconds.
 8. The method of claim1, wherein the physical channel comprises a Physical Downlink ControlChannel (PDCCH), the method further comprising: detecting a downlinkcontrol indicator (DCI) message received on the PDCCH, the DCI messageincluding one or more bits associated with a cyclic redundancy check(CRC), the CRC bits of the DCI message scrambled by a TDD-Radio NetworkTemporary Identifier (TDD-RNTI) that contains TDD configurationindicator; descrambling the scrambled CRC based, at least in part, on aTDD-Radio Network Temporary Identifier (TDD-RNTI) to identify the CRCbits and an associated payload; and identifying a TDD configurationindicator in the associated payload, wherein the TDD UL/DL allocation isupdated in accordance with the TDD configuration indicator.
 9. Themethod of claim 8, wherein the DCI message is received from a commonsearch space of the PDCCH.
 10. The method of claim 8, wherein the TDDconfiguration indicator identifies a specific TDD configuration.
 11. Themethod of claim 8, wherein the TDD configuration indicator identifies achange in an existing TDD configuration.
 12. A user equipmentcomprising: a processor configured to receive an indicator, from anenhanced NodeB in the LTE network, on a physical channel, identifying atime division duplex (TDD) configuration for the UE; and the processorfurther configured to automatically update the TDD uplink (UL) anddownlink (DL) allocation of the UE in accordance with the TDDconfiguration.
 13. The user equipment of claim 12, wherein the physicalchannel comprises a Physical Control Format Indicator Channel (PCFICH),and the processor is further configured to: identify a scrambled ControlFormat Indicator (CFI) based, at least in part, on the received PCFICH;and descramble the scrambled CFI to identify the CFI and a TDDconfiguration change indicator, wherein the TDD UL/DL allocation isupdated in accordance with the TDD configuration change indicator. 14.The user equipment of claim 12, wherein the physical channel comprises aPhysical Downlink Control Channel (PDCCH), the processor furtherconfigured to: detect a downlink control indicator (DCI) messagereceived on the PDCCH, the DCI message including one or more bitsassociated with a cyclic redundancy check (CRC), the CRC bits of the DCImessage scrambled by a TDD-Radio Network Temporary Identifier (TDD-RNTI)that contains TDD configuration indicator; descramble the scrambled CRCbased, at least in part, on a TDD-Radio Network Temporary Identifier(TDD-RNTI) to identify a CRC and an associated payload; and identify aTDD configuration indicator in the associated payload, wherein the TDDUL/DL allocation is updated in accordance with the TDD configurationindicator.
 15. A method for configuring a Time Division Duplex (TDD)Uplink/Downlink (UL/DL) allocation of a user equipment (UE) in a LongTerm Evolution (LTE) network, comprising: identifying a TDDconfiguration change; and transmitting an indicator, from an enhancedNodeB in the LTE network, on a physical channel, identifying a TDDconfiguration for the UE.
 16. The method of claim 15, wherein thephysical channel comprises a Physical Control Format Indicator Channel(PCFICH), the method further comprising: scrambling a Control FormatIndicator (CFI) based, at least in part, on the received PCFICH.
 17. Themethod of claim 15 wherein the physical channel comprises a PhysicalDownlink Control Channel (PDCCH), the method further comprising:identifying a TDD configuration indicator, the TDD configurationindicator indicating a TDD configuration for a UE; scrambling one ormore bits associated with a cyclic redundancy check (CRC) of a downlinkcontrol indicator (DCI) message based, at least in part, on the TDDconfiguration indicator; and transmitting the DCI message using thePDCCH.
 18. An apparatus for configuring a Time Division Duplex (TDD)UL/DL allocation of a user equipment (UE) in a Long Term Evolution (LTE)network, comprising: a processor configured to identify a TDDconfiguration change; and the processor further configured to transmitan indicator, from an enhanced NodeB in the LTE network, on a physicalchannel identifying a TDD configuration for the UE.
 19. The apparatus ofclaim 18, wherein the physical channel comprises a Physical ControlFormat Indicator Channel (PCFICH), the processor further configured toscramble a Control Format Indicator (CFI) based, at least in part, onthe received PCFICH.
 20. The method of claim 18, wherein the physicalchannel comprises a Physical Downlink Control Channel (PDCCH), theprocessor further configured to: identify a TDD configuration indicator,the TDD configuration indicator indicating a TDD configuration for a UE;scramble one or more bits associated with a cyclic redundancy check(CRC) of a downlink control indicator (DCI) message based, at least inpart, on the TDD configuration indicator; and transmit the DCI messageusing the PDCCH.